These proceedings contain the papers of the 15th International Conference on e-Learning (EL 2021), which was organised by the International Association for Development of the Information Society (IADIS), July 20-22, 2021. This conference is part of the 15th Multi Conference on Computer Science and Information Systems (MCCSIS), July 20-23, 2021,…

With a significant increase in the number of e-learning resources the issue of quality is of current importance. An analysis of existing scientific and methodological literature shows the variety of approaches, methods and tools to evaluate e-learning materials. This paper proposes an approach based on the procedure for estimating parameters of…

By means of a simple mathematical model developed by the authors, the apparent movement of the Sun can be studied for arbitrary latitudes. Using this model, it is easy to gain insight into various phenomena, such as the passage of the seasons, dependences of position and time of sunrise or sunset on a specific day of year, day duration for…

This volume contains papers submitted to the 12th Annual International Conference of the Bulgarian Comparative Education Society (BCES), held in Sofia and Nessebar, Bulgaria, in June 2014, and papers submitted to the 2nd International Partner Conference, organized by the International Research Centre 'Scientific Cooperation,' Rostov-on-Don,…